1. Field of Invention
This invention discloses water absorbent polymer articles and a process for their production. More particularly, the invention discloses a latex polymer foam containing both a water absorbent polymer and chitosan (chitin) (hereinafter reference to "Chitin" or "Chitoson" will include both) within its structure.
2. Prior Art
Recently there has been interest in producing products which are highly absorbent of aqueous fluids, particularly blood and exudate, as drying materials, wound dressings, and chromatographic materials and for other similar uses. Some of the prior art materials used to form these products have been non-woven fabrics, papers, pulps, spongy urethane resins, natural sponges and the like. However, these materials exhibit relatively low water absorbency, thus failing to satisfy the need for a low volume, highly water absorbent product.
Substitutes for these materials such as cross-linked polyethylene oxides, cross-linked polyvinyl alcohols and hydrolyzed products of starch-polyacrylonitrile-grafted polymers have recently appeared on the market. While these products do show increased water absorbency, it is still not sufficiently high to justify the increased costs and difficulty of production. In addition, some of these materials create disposal problems because they are not biologically degradable.
Japanese Patent Application Kokai, No. 57-92,032 (1982) discloses a polyurethane foam that contains a useful water absorbent polymer wherein the size of the water absorbent resin is in the range from about 200 to 400 microns.
A biodegradable, highly water absorbent resin is disclosed in U.S. Pat. No. 4,076,663. While the resins of this patent do show increased water absorbency, their use has been limited to mixing them in sanitary napkins, diapers and other such products wherein the resins are used in their particulate or powder form.
U.S. Pat. Nos. 4,454,268, 4,337,181 and 4,133,784 disclose various types of films partially comprised of water absorbent polymers. These patents disclose starch-based, water absorbent polymers prepared from a combination of starch and ethylene acrylic acid copolymers.
U.S. Pat. No. 3,669,103 discloses water swellable, water insoluble polymeric sorbents for the absorption of aqueous fluids wherein said polymeric sorbents are lightly cross-linked polymers. This patent discloses the use of a polyurethane foam as a support for the polymeric absorbent.
Latex materials, particularly latex foams have been well known for many years. For example, the largest single use of latex today is in foam rubber. Latex foams are frequently used in mattresses, pillows, seat cushions, carpet backing and textile foam laminates. Latex foams also find use as cushioning in many types of fabrics such as athletic clothing.
There are numerous processes for the production of latex foams. See for example, U.S. Pat. Nos. 3,650,995, 4,205,103, and 4,174,415. While numerous latex foam patents exist, none disclose the use of a latex foam containing within its structure both a cellulose-based water absorbent polymer and chitin or a process for production of such a material.
One of the newest uses for super absorbent materials is as a wound dressing or covering for injuries. Chitin or its deacylated form, chitosan, have also been useful as biopolymeric powders to assist in the treatment of wounds and injuries. Chitosan is a glucosaminoglycan which is a major constituent of the shells of shrimp, crabs and lobsters, the cell walls of filamentous fungi and the exoskeletons of insects. The use of chitosan as a biopolyermic powder has been described, for example, by several patents by Balassa. See U.S. Pat. Nos. 3,903,268, 3,911,116 and 3,914,413. Other patents disclosing the use of chitosan and describing some of its properties include U.S. Pat. Nos. 4,018,678, 4,609,470, 4,613,502 and 4,659,700.
In the medical field chitosan powder acts as a biopolymeric regeneration material. It very slowly depolymerizes in a wound with its monomeric components efficiently entering into a metabolic reaction in the wound. The powder contributes in this way to the regeneration of damaged skin tissue.
Because of the biopolymeric features of chitosan, it is not surprising that it has been combined with various materials specifically for use as wound dressings. For example, U.S. Pat. No. 4,460,642 discloses the use of a polytetrafluorethylene fibril matrix which contains hydrophilic absorbents including chitin and chitosan.
The use of chitosan with gelatin to form a surgical dressing or wound dressing to assist the healing process is also disclosed in U.S. Pat. No. 4,572,906. The combination of a polyvinyl alcohol with a chitosan salt to produce a film is disclosed in U.S. Pat. No. 3,962,158. Other references to the use of chitosan with other types of material to form wound dressings are disclosed, for example, in U.S. Pat. Nos. 3,632,754 and 4,570,629.
While all of these chitosan patents disclose the use of chitosan in combination with certain conventional materials for the production of wound dressings and other surgical materials, none disclose its combination with a super absorbent polymer which is bound into a latex foam. The combination of these materials provides significantly improved materials over prior art products.
Accordingly, it is an object of this invention to prepare latex foams containing within their structure both water absorbent polymers and chitin biopolymers.
It is a further object of this invention to disclose water absorbent latex foams which contain both water absorbent polymers and chitin biopolymers within their structure which are useful for the absorbance of fluids while retaining the shape of the latex foam.
It is a still further object of this invention to disclose a process for preparing latex foams containing both water absorbent polymers and chitin biopolymers wherein the latex foam has secured thereto a backing to form a water absorbent latex foam laminate containing chitin.
It is a still further object to this invention to disclose a process for preparing a latex foam containing both water absorbent polymers and chitin biopolymers which can be useful as wound or surgical dressings.
These and other objects, as well as the scope, nature, and utilization of this invention, will be apparent from the following detail description.